Closure operating mechanism



Dec. 14, 1965 B. w. TUCKER, JR 3,223,403

CLOSURE OPERATING MECHANISM Filed May 25. 1963 BEN/#Mw warf/fava rua/5A JA.

mv E N Td n BY ArVrowmsYA United States Patent O 3,223,403 CLOSURE GPERATNG MECHANSM Benjamin Whitehead Tucker, Jr., South Orange, NJ., as-

signor to Otis Elevator Company, New York, NSY., a corporation of New Jersey Filed May 23, 1963, Ser. No. 282,758 9 Claims. (Cl. 268-53) This invention pertains to an operating mechanism and more particularly to an operating mechanism for elevator doors or closure.

It is advantageous in elevators to employ an electric motor in conjunction with a speed reduction mechanism to provide low torque output for operating car and hatchway doors. ln the event of power failure for operating the motor, it is desirable to be able to manually open the door or closure means. Because of the conventional cumbersome arrangements in the speed reduction and operating mechanism, which permits manual opening of the door in emergencies, it was frequently necessary to employ some means of disengaging the door from the operating motor.

The speed reduction mechanisms heretofore employed, generally included one of several methods, namely, a gear train, a rack and gear, a lever arrangement, or a belt system. All of these mentioned conventional operating mechanisms have undesirable features, in that they are ordinarily very bulky and require large installation space, generally are noisy, require frequent maintenance and repair, and are costly to manufacture and maintain. A rack and gear system would have to be enclosed for properly lubricating same, whereas this invention uses a coupling of self-lubricating roller chain, further reducing cost and noise of the conventional coupling unit for multi-stage speed reduction.

The present invention eliminates practically all of the undesirable features heretofore found in door operating mechanisms in that it provides a compact device which is small in size yet robust, operates quietly, provides a unique two-stage speed reduction arrangement, and an eilcient door cushioning device operatively combined as a composite assembly.

An advantage or object of the present invention is the use of a worm-gear drive from the motor to provide approximately one half of the speed reduction with quiet operation, while permitting the installation of the drive motor with its axis parallel to the threshold of the elevator car instead of projecting toward the center of the car, thus allowing more room for installation of other equipment on the top of the car, and for a more suitably located overhead emergency exit. Furthermore, the worm-gear drive permits a large lead angle of the driving worm to be used thus enabling the door to be opened from the inside in the event of power failure. The other half of the speed reducing apparatus is a quiet operating chain-coupled segment and sprocket considered as two rocking levers to provide a speed reducing second stage lever arrangement.

Another advantage or object of the present invention is that the door cushioning device is integral with the lever segment and door operating arm, and attains a reduction in the number of parts to provide a more positive operation in cushioning of the doors. The door cushioning device is of the rotary type and reduces probability of oil leakage, is quiet in operation, employs a tapered bleeder channel for continuously increasing torque as the closure or door reaches each of its operating extremities to reduce impact of the closure operation at a controlled rate by the bleeder opening varying in size during operation, and also provides independent adjustable valves for door cushioning control in each direction of closure operation.

Another object or advantage is to provide a door operating device having a drive motor coupled to a combination two-stage gear-rocking lever speed reducing unit with the output thereof directly coupled to an integral rotary hydraulic cushioning device to provide a compact assembly or unit in a system which permits manual opening of the door in case of power failure Without altering or disconnecting the normal door operating mechanism.

Another object of the invention is to provide an elevator closure actuator or operating mechanism including a two-stage speed reduction arrangement embracing a worm and worm-gear for providing about one half of the speed reduction, and a rocking sprocket and chainoperated rocking lever or segment for providing approximately the other half of the speed reduction to permit the door to be opened without disengaging either of the speed reduction mechanisms from the system.

A further object is to provide a rocking lever or segment and a two-way cushioning device as an integral unit being chain-driven by a sprocket operating from a driving Worm having a relatively long lead angle and a worm gear to minimize the force required to turn back the worm and motor by way of Operating the lever segment when needed for servicing or emergency use.

Another object is to provide a novel door operating system that is positive operating but capable of permitting the door or doors to be manually opened without altering any of the machinery or coupling arrangement, yet be highly efcient, relatively quiet in operation, and manufactured at a greatly reduced cost.

The present invention contemplates a door operating mechanism as a compact assembly unit comprising a drive motor coupled to a two-stage speed reduction mechanism and a door cushioning unit. The speed reduction mechanism utilizes a first stage gear reduction unit comprising a worm and worm-gear having approximately a 10 to l ratio speed reduction with the motor, and a second stage as a sprocket and chain-operated lever segment, both coupled together and considered as a rocking lever arrangement also having approximately a l0 to 1 ratio speed reduction, relative to the output shaft of the gear reduction unit. The lever segment per se is operated by a sprocket driven chain and is pivoted directly on the shaft of an integral two-way rotary hydraulic cushioning device. The cushioning device has opposed pistons to provide twoway variable resistive torque, being more pronounced as the door travels in the extreme areas to its open and closed limits, and also has adjustable valves for independent cushion control for door operation in each direction.

The invention will be described as applied to an elevator door with the power driven mechanism arranged to open and close the door or doors. It is Within the scope of this invention to utilize this closure operator with any of the sliding type elevator doors. Other advantages of this invention will be apparent from the following description of the preferred embodiment.

In the drawings: f 3

FIGURE l is a schematic elevational view of a preferred embodiment of the invention, mounted in position for opening and closing a sliding type elevator door;

FIGURE 2 is an enlarged fragmentary side elevation, as viewed from the left of FIGURE 1;

FIGURE 3 is an enlarged front elevation of the door operator having parts broken away, and with the operating arm in vertical position;

FIGURE 4 is a front elevational view of the cushioning mechanism with portions broken away;

FIGURE 5 is a sectional view along line 5-5 of FIGURE 4;

FIGURE 6 is a view along line 6-6 of the plunger and lever arm of FIGURE 4; and

FIGURE 7 is a detailed showing of the rocking leveroperated speed reduction second stage with its rocking sprocket secured on the shaft of the worm gear of the speed reduction rst stage.

Referring to the drawings and more particularly to FIGURES 1, 2 and 3, there is shown an elevator car or cab 20 having framework 21 with a top 22. A sliding door 24 is shown in a closed position in solid lines to the right of the cab while the same door is shown in the open position in dotted lines 24' to the left. A track bracket 26 in the form of a structural angle iron is secured to the top framework of the cab 20 and extends approximately the full width of the cab. It is secured to the framework by bolts 28, FIG. 2. A door track 30 is spaced from the bracket 26. Accordingly, the track is parallel to the track bracket substantially the full width of the car to permit movement of the door hanger rollers. The door 24 has an integral metal door hanger 36 nearly the width thereof extending upwardly therefrom. Door hanger rollers 38 are pivoted by pins 40 to the door hanger 36 to permit the door hanger rollers to engage the top of the track and allow the door to be moved freely from its closed to its open position. The door hanger rollers are flanged as guides on either side thereof by opposed anges 41 to retain the rollers aligned on the track. An assembly bracket 42 extends upwardly from and is secured to the track bracket 26 by bolts 43, with the assembly bracket extending above the top of the cab to support thereon the operating mechanism connected to the operating arm for the door.

The larger components of the door operating mechanism carried by the assembly bracket 42 includes a motor 44, supported by and directly coupled to a gear reducing unit 45, and is secured to a pair of opposed flanges 46 mounted on the mounting bracket 42. A twoway rotary hydraulic cushioning unit 47 is secured by bolts 48 to the mounting bracket 42 below the gear reducing unit 4S.

A lever segment 49 is mounted by way of a depending arm 23 on a plunger lever shaft 50 rotatably mounted within the housing 51 having a removable sealing cap 51' fastened thereon, and forming the cushioning unit 47. An operating arm 52 used for movement of the door is secured to the lever segment depending arm 23 by bolts 53' which are positioned above and below the lever shaft 50. The lower free end of the operating arm 52 is connected to a pivot pin 53 which connects to one end of an operating link 54, while the other end of said operating link is pivoted by a pin 55 to a mounting plate 60 on the door.

From the above it will be seen that rocking of the lever segment 49 on the shaft 50 mounted in the cushioning unit 47 will cause the door 24 to be moved from its fully closed position, as shown in solid lines, in FIGURE 1, to its fully open position as shown by the dotted lines in FIGURE 1.

-The motor shaft has a drive worm 61 formed as an extension of the motor shaft, and projects into the housing of the gear reducing unit 45. A wormgear 62 is secured to the sprocket shaft 63 carried by the speed reducing unit housing with a portion of the shaft 63 extending -outwardly of the unit 45 and having a sprocket 64, secured on said shaft 63 to permit the sprocket 64 to be rotated by rotation of the motor driven worm and worm gear.

A roller chain 65 fits in an arcuate chain channel 66 which extends approximately 180 around the peripheral edge of the lever segment 49 with its chain ends adjustably connected thereto. The channel 66 prevents the chain from being laterally displaced so that it is retained substantially in alignment with the plane of the segment 49 and the sprocket 64. The sprocket is disposed close to but spaced from the lever segment 49, and is aligned in a plane so that the roller chain will engage the sprocket teeth on the edge of the sprocket away from the segment, while the free ends of the chain are adjustably secured by fastening means to the opposed segment ears 67, of which there are two. The fastening means on each end of the chain consist of a threaded rod 68 having one end thereof connected by a pin 69 to its respective end of the chain. Each threaded rod 68 slidably ts through a complemental hole in its respective segment ear, and each rod is retained in position by a nut 29 for compressing a cylindrical rubber cushion 70 between a pair of spaced metallic washers 27, so that tightening of the adjustment means nuts 29 will take up the slack in the chain that fits over the sprocket so that there is virtually no looseness or slack in the chain when it is properly secured to be operated by rotation of the sprocket. The rubber cylindrical cushions 70 provide a shock absorber effect and slack take-up means for the chain to keep the chain under controlled tension. The tension becomes variable during operation; as tension decreases on one end of the chain and simultaneously increases on the opposite end, depending on whether the door is being opened or closed, and finally the tension is again balanced as the door stops moving.

The two-way rotary hydraulic cushioning unit 47 has a lhousing 51 which has a bore formed therethrough for receiving a double ended piston or plunger 71. The bore goes completely through the housing. Pipe plugs are threadedly connected into the housing as closures at either end of the bore. As previously set forth, the lever segment 49 is mounted on one end of a shaft 50 mounted in the housing 51 of the cushioning unit so that rocking of the segment 49 will cause the shaft 50 to be also rocked for operating a plunger lever 73 secured on the shaft 50 by a key 74. The plunger lever 73 is forked on one end and has a hole therethrough to receive shaft 50. A bolt 76 through the forked fingers 76' and 76" may be tightened to compress said fingers and hold the plunger lever in a fixed position to prevent longitudinal and rotational movement of the lever 73 on the shaft 50, to cooperate with the shaft locking key 74 in the shaft 50, which prevents the plunger lever 73 from rotating on the shaft 50. The opposite or free end of the flat metal plunger lever 73 has a circular lever head 77 which ts in a lever recess or slot 78, formed in the central portion of the double ended plunger 71. The peripheral edge of the circular lever head 77 engages the opposed inner Surface portions of the recess or slot 78 which surface portions form the inner ends of the double ended plunger 71, having both a left plunger and a right plunger as shown in FIGURE 4, with both plungers being allochiral. A tapered V slot bleeder 79 is formed in each plunger portion and is larger at the outer end than at the inner end, which taper decreases toward the slot 78 until it merges with the full diameter of the plunger to provide variable torque or fluid ow at a variable rate.

In FIGURE 5 it will be seen that the recess or slot 78 midway between the extremities of the double ended plunger 71 receives the plunger lever 73 which actuates both plungers simultaneously, since they are a unitary element, united by less than one half of the cross-section of the element 71, indicated as area 93, which portion remains after the slot 78 is formed. There is a through passageway 80A formed longitudinally in each of the plungers or plunger portions 71A and 71B, with the inner `ports of the passageways each terminating in the transverse opposed surfaces of the plunger recess or slot 78 adjacent but spaced laterally from the lever head 77 as seen in FIGURE 5 to prevent obstruction thereof. A check valve 81 in the form of ya ball may engage its respective shoulder, which is a check valve Iball seat 82(A). A retaining pin 7S is disposed in each of the passageways 84) (A and B) but spaced away from the check valve or ball to allow the ball to be seated or unseated relative to the respective ball seat or shoulder 82A as liquid flows through its respective passageway 80 during normal operation of the device. The bore for both pistons or plungers communicates with a respective port 84 for each plunger, which bore edge actually forms a seat for the stem of the adjustable valve 85, which valve controls the fluid flow through the respective passage 86 into the interior of the housing above the respective plungers as the cushioning device operates in accordance with the opening and closing of the closure means or door, and provides a parallel huid outlet with its complemental bleeder 7 9.

For convenience the reference characters may, in some instances, have a letter (A) or (B) appended thereto, to more precisely indicate the corresponding or allochiral parts, respectively. For example, 85(A) refers to the adjustable valve 85 shown on the left side in the drawings, and 85(13) refers to the corresponding adjustable valve, in the form of a screw-headed valve stem, on the right side, as in FIGURE 4.

When the lever segment 49 rocks so that the lever head 77 of the cushioning unit moves to the left, as shown in FIGURE 4, and urges the plunger accordingly, oil, which normally fills about half of the housing, will be urged ahead of the left plunger, and ball 81,(A), as the ball engages its complemental ball seat. In operation, the oil flows through two different paths in each direction, into the housing, namely through the tapered bleeder 79, and also through the opening 86 at adjustable valve 85. Since the tapered bleeder arrangement decreases the size of the oil outlet 79 as the plunger moves to the left, there will be increased resistance, or torque, to the movement, or rocking of the lever head 77 to the left, thereby slowing down the rocking action of the lever head and accordingly slowing down, or cushioning, the rocking action as the lever segment operating arm actuates the door.

Accordingly, as the lever head 77 moves to its eX- treme left position, the opening operation of the door will -be slowed down continuously, at a controlled rate, until maximum resistance of the -cushioning unit is in effect, and the door comes gently and quietly to -a fully opened position. The same operation of the plunger, but in the opposite direction, provides a continuously changing resistive torque as the plunger lever head 77 moves to the right, or to the fully closed position of the door. The cushioning control valves 85 (A and B) may be adjusted to provide the controlled amount of bleed off through the valves to afford the desired resistive action in the cushioning of the door clos-ing and opening operations. The fluid flow control means of the cushioning unit includes the adjustable valves 85 (A and B) which control the amount of cushioning of the impact of the closure means, and the tapered bleeder means which have a relatively large area at one end and a smaller area, to zero area, at the other end, control the variable rate of cushioning.

In one preferred form for a particular elevator installat-ion, t-he two-stage speed reducing unit employs, in one stage, a worm and worm gear, having .a 10 to 1 ratio, which was coupled to a second stage with a rocking lever-segment arrangement having a 10 to 1 ratio. However, a two-stage speed reducing unit may have the first stage worm and worm gear unit operating in the range from 6 to 1 ratio up to 12 to 1 ratio, and the second stage rocking sprocket-segment also operating in the range from 6 to 1 ratio up to 12 to 1 ratio, with satisfactory turning back of the motor by operating the elevator door. The ratios selected for a particular twostage speed reduction arrangement would depend on the particular results desired, with the longer lead angle of the worm gear minimizing the force required to turn back the motor by operating the door manually,

The cushioning effect, due essentially to the rotary cushioning unit, is more particularly noticeable in the extreme areas of door opening and closing, which is positive operating yet quiet and very gentle. Controlled torque is employed also by micro-switch 94 secured on the mounting bracket 42, and engageable by a cam 95 carried on the rocking lever-segment 49, to include a resistor in the drive motor electrical circuit, at a precise point in the door closing operation to reduce the applied voltage to the drive motor and thereby reduce the driving motor torque to coincide with the extreme cushioning unit effect to facilitate the door closing positive operation and quietness. The tapered bleeders of the rotary cushioning device provide hydraulic cushioning with constantly changing resistive torque as the door travels to its open and its closed limits of operation.

The representative showing of a 10 to 1 ratio wormworm gear, or first stage speed reduction gear arrangement, and the 10 to 1 ratio sprocket lever-lever segment, or second stage speed reduction rocking lever arrangement are operatively coupled by way of the shaft 63. The sprocket and segment of the second stage are coupled to each other by a single length of roller link chain under tension engaging the top toothed portion of the sprocket, with the opposite free ends of the chain each resiliently coupled to the end portions of the lever segment. The chain coupling of the sprocket and segment operates quietly, yet is positive in function with no slack in the chain, and is resiliently mounted as a chain take-up means to minimize the noise of motion-termination impact and shock.

In FIGURE 7, there is shown one representative arrangement of sprocket and segment, or rocking levers. The sprocket 64 represented has a one inch (1) pitch radius. The lever segment 49 mounted on the plunger lever shaft 50 is eight and three-fourths (8%) inches from the bottom of the segment channel 66 to the center of the shaft 50, while the roller 65' of the roller chain 65, is one-half (1/2) inch in diameter with a quarter (MW) inch radius having a center line indicated by the broken arcuate line R. Accordingly, the pitch radius of the lever segment and roller is (83% plus MW) or nine (9) inches.

Speed reduction is determined by the ratio of the pitch radius of the driving shaft sprocket which is 0.9 inch, to the radii of the driven shaft lever segment which is 9.0 inches. Therefore the speed reduction ratio of the rocking lever system presented in FIGURE 7, comprising the sprocket or sprocket rocking lever 64 and the rocking lever segment 49, is 10 to l.

From the foregoing it should be apparent that the chain coupling operation between the two rocking elements of the second stage of the speed reduction mechanism, namely the rocking sprocket and the rocking segment is virtually noiseless. The take-up arrangement of the chain adjustment means provides positive interlinking of the sprocket and segment by a self-lubricating roller chain affording smooth compression and release of the cylindrical rubber cushions 70, that virtually absorb all shock, and eliminate noise.

The door operator device represents an optimum arrangement for a positive action door oeprating mechanism, that is free from lock-up condition by permitting the door or doors to be immediately manually operated in event of power failure. Further, the entire device is a composite assembly of a motor, a two-stage speed reducing unit comprising a worm-worm gear first stage, and a rocking lever second stage, operatively coupled to an integral two-way rotary hydraulic cushioning device carrying a rocking lever segment as part of the speed reducing unit second stage. The invention provides a compact door operating assembly having minimum space requirement, that is positive operating, conveniently installed in a small space, virtually noiseless in operation, practically service free, and greatly reduced in cost of manufacture.

As many changes can be made in the above described construction and many apparently different embodiments of this invention can be made without departing from the scope thereof, it is intended that all matter contained in the above description or shown on the accompanying drawings be interpreted as illustrative only and not in a limiting sense.

What is claimed is:

1. A compact closure operating unit for actuating a closure for an elevator comprising, a driving motor, a two-stage speed reducing assembly having a worm and worm-gear first stage and a chain-coupled sprocket and segment second stage, and a cushioning device, including an operating shaft, for minimizing impact of said closure, said shaft being fastened to said segment to constitute a pivot therefor.

2. A compact closure operating unit for actuating an elevator closure as set forth in claim 1, wherein said worm, said worm gear and said sprocket are mounted as a rst unit on an assembly bracket, and wherein said cushioning device and said segment are mounted as a second unit on said bracket, with t-he plane of the sprocket and the plane of the segment being substantially aligned, and wherein the chain of the chain-coupled sprocket and segment engages the toothed edge of the sprocket away from the segment and wherein opposite chain ends are affixed to the respective opposite end portions of said segment for operating said hydraulic cushioning device.

3. A compact closure operating unit for actuating an elevator closure as set forth in claim 2, wherein said opposite ends of said chain are afiixed to said opposite end portions of the segment by resilient mounting means that retain said chain normally under tension and which tension is variable under closure actuating conditions.

4. An operating mechanism for an elevator door, comprising,

a motor,

a two stage speed reducing assembly operatively connected to said motor,

said assembly comprising a worm and worm gear first stage and a chain coupled sprocket and segment second stage,

an arm fastened to said segment for opening and closing said door, and

a two way hydraulic cushioning device including an operating shaft,

said segment being fastened to said shaft,

whereby operation of said motor swings said arm to operate said door and rotates said shaft to operate said cushioning device.

5. An operating mechanism for an elevator door, comprising,

amotor,

a two stage speed reducing assembly operatively connected to said motor,

said assembly comprising a worm and worm gear first stage and a chain coupled sprocket and segment second stage,

an arm fastened to said segment for opening and closing said door, and

a hydraulic cushioning device comprising,

a housing,

an operating shaft rotatably mounted in and eX- tending to the exterior of said housing, and

means for imparting resistance to the rotation of said shaft, which resistance increases as said shaft rotates further in either direction from an intermediate position,

said segment being fastened to said shaft,

whereby operation of said motor swings said arm to operate said door and rotates said shaft to operate said cushioning device.

6. An operating mechanism for an elevator door, comprising,

a motor,

a two stage speed reducing assembly operatively connected to said motor, said assembly comprising a worm and worm gear first stage and a chain coupled sprocket and segment second stage, an arm fastened to said segment for opening and closing said door, and a hydraulic cushioning device, comprising a tiuid filled cylinder, a double ended plunger positioned in said cylinder defining chambers at opposite ends thereof, an operating shaft, means for imparting linear motion to said plunger in response to rotary movement of said shaft, and adjustable means for restricting the escape of fluid from said chambers, said segment being fastened to said shaft, whereby operation of said motor swings said arm to operate said door and rotates said shaft to operate said cushioning device. 7. An operating mechanism for an elevator door, comprising,

a motor, a worm driven by said motor, a worm gear driven by said Worm, a sprocket driven by said worm gear, a lever formed with an arcuate segment on one end and a depending arm on the other end, a chain having opposite ends thereof fastened to spaced apart points on said arcuate segment, said chain operatively engaging and being driven by said sprocket, an operating arm fastened to said depending arm for opening and closing said door, and a two way hydraulic cushioning device, including an operating shaft, for cushioning the terminal movement of said door, said operating shaft being fastened to said lever to constitute the pivot therefor, whereby rotation of said motor swings said operating arm to move said door and rotates said shaft to operate said cushioning device. 8. An operating mechanism for an elevator door, comprising,

a motor, a worm driven by said motor, a worm gear driven by said worm, a sprocket driven by said worm gear, a lever formed with an arcuate segment on one end and a depending arm on the other end, a chain having opposite ends thereof fastened to spaced apart points on said arcuate segment, said chain operatively engaging and being driven by said sprocket, an operating arm fastened to said depending arm for opening and closing said door, and a double acting hydraulic cushioning device for cushioning the terminal movement of said door, said device comprising,

a housing, an operating shaft rotatably mounted in and extending to the exterior of said housing, and means for imparting resistance to the rotation of said shaft, which resistance increases as said shaft rotates further in either direction from an intermediate position,

said operating shaft being fastened to said lever to con` stitute the pivot therefor, whereby rotation of said motor swings said operating arm to operate said door and rotates said shaft to operate said cushioning device. 9. An operating mechanism for an elevator door, comprising,

a motor,

a worm driven by said motor, a worm gear driven by said worm, a sprocket driven by said worm gear, a lever formed with an arcuate segment at one end and a depending arm at the other end, a chain having opposite ends thereof fastened to spaced apart points on said arcuate segment, said chain operatively engaging and being driven by said sprocket, an operating arm fastened to said depending arm for opening and closing said door, and a double acting hydraulic cushioning device, said device comprising,

a housing, a cylinder formed in said housing, a double ended plunger positioned within said cylinder, iluid within said cylinder, an operating shaft rotatably mounted in and eX- tending to the exterior of said housing, means interconnecting said shaft and said plunger for imparting linear movement to said plunger in response to rotary movement of said shaft, each end of said plunger being formed with a passageway therethrough, a one Way check valve in each of said passageways for controlling the ow of fluid through its associated passageway,

each end of said plunger being formed with a tapered V slot hleeder passageway, said cylinder being formed with a pair of escape passageways for said fluid, one adjacent to each end of said cylinder, and valve means in each of said escape passageways for controlling the rate of flow of uid therethrough, said operating shaft being fastened at a point exterior of said housing to said lever to constitute the pivot therefor, whereby operation of said motor swings said operating arm to operate said door and rotates said shaft to operate said cushioning device.

References Cited by the Examiner UNITED STATES PATENTS 615,707 12/ 1898 Horsfeld 16-56 1,594,513 8/ 1926 Ainsworth 268-49 1,770,250 7/1930 Norton 16-56 2,003,399 6/ 1935 Tamsitt. 2,458,402 1/ 1949 Myers 26S-53 2,890,881 6/1959 Tucker 268--53 25 LOUIS J. DEMBo, Primary Examiner.

SAMUEL F. COLEMAN, Examiner. 

1. A COMPACT CLOSURE OPERATING UNIT FOR ACTUATING A CLOSURE FOR AN ELEVATOR COMPRISING, A DRIVING MOTOR, A TWO-STAGE SPEED REDUCING ASSEMBLY HAVING A WORM AND WORM-GEAR FIRST STAGE AND A CHIN-COUPLED SPROCKET AND SEGMENT SECOND STAGE, AND A CUSHIONING DEVICE, INCLUDING 